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Applied Surface Science (v.256, #3)

Current trends in nanostructured polymer and sol–gel thin films by James Rohan Guest Editor (pp. s1-s2).

Decorative a-C:H coatings by F. Černý; V. Jech; I. Štěpánek; A. Macková; S. Konvičková (pp. s77-s81).

a-C:H coatings on stainless steel sheets were prepared for decorative purposes by RF PACVD method. The silicon and nitrogen were introduced into coatings for improving adhesion. Adhesion was tested by scratchtest and by static indentation. Hardness was investigated by nanoindentation. Chemical composition of coatings was measured by ERDA. Coatings with thickness 1.3μm have approximately the same morphology as the substrate.

Keywords: PACS; 81.15.−za-C:H films; RF PACVD; Decorative coatings; Adhesion

Microfabrication process for patterning metallic lithium encapsulated electrodes by Sami Oukassi; Nicolas Dunoyer; Raphael Salot; Steve Martin (pp. s58-s60).

This work presents recent achievements concerning thin film encapsulation of metallic lithium negative electrode. In the context of this study, the encapsulation stack includes polymer and dielectric layers combined in such way to optimize barrier performances of the whole structure towards oxygen and water vapor permeation. The first part of this work is dedicated to the description of the barrier stack architecture and properties. A second part presents the application of a microfabrication process to the metallic lithium negative electrode and barrier stack so as to have very small features (100μm×100μm patterns). The microfabrication process includes several steps of photolithography and etching (dry and wet) blocks, which allows us to reach the target critical dimensions. These results show a method of patterning functional metallic lithium. It demonstrates the feasibility of energy sources miniaturization which is an important issue in the field of autonomous and wireless sensor networks.

Keywords: PACS; 82.47.AaLithium electrode; Photolithography; Microbatteries; Microfabrication

Defect-free nanostructured alumina coating doped with noble metal nanoparticles by Miroslava Malenovska; Marie-Alexandra Neouze; Ulrich Schubert; Veronique Monnier; Emmanuel Scolan; Raphael Pugin (pp. s9-s11).

Nanostructured alumina coatings loaded with platinum or gold nanoparticles were prepared by two different methods. In the first method the alumina coatings were prepared in the presence of metal ions, which were reduced using UV irradiation once the film was deposited. In the second method, polyvinylpyrrolidone-stabilized nanoparticles were first synthesized and then incorporated in the coating. The texturation of the coating occurred in a last step by hot water treatment.

Keywords: Alumina coating; Metal nanoparticles; Surface nanotexturation

Isotactic polypropylene modified with clay and hydrocarbon resin: Compatibility, structure and morphology in dependence on crystallization conditions by Sossio Cimmino; Donatella Duraccio; Clara Silvestre; Marilena Pezzuto (pp. s40-s45).

The influence of a based montmorillonite (MMT) clay on the phase structure, structure, morphology and crystallization behaviour of iPP is investigated. A low molecular mass hydrocarbon resin, containing hydroxyl and acid groups, suitable to interactions probably through hydrogen bonding with the polar surface of the clay, was also added to iPP/clay system with the aim to increase the compatibility between iPP and clay and then to improve the performance of such nanocomposites. The crystallization conditions as well as the blend formulation dictate the phase structure, the clay interlayer distances and the iPP polymorphism. In the ternary system intercalation and probably exfoliation of clay layers can be obtained in dependence on thermal treatments. These results open new perspectives to the preparation of homogeneous polypropylene clay nanocomposites and can be the base for further investigation aiming at optimizing the nanomaterials processing conditions.

Keywords: PACS; 61.46.−w; 81.07.bIsotactic polypropylene; Clay; Oligomer; Structure–properties relationship; Compatibility

Mesoscopic objects, porous layers and nanocomposites—Possibilities of sol–gel chemistry by Ireneusz Piwoński (pp. s86-s91).

The goal of this study was to prepare mesoscopic objects, thin porous films and nanocomposite coatings with the use of sol–gel technique. Silica nanotubes, titania nanoparticles, porous titania and zirconia coatings as well as titania nanocomposites were successfully synthesized by changing the type of sol–gel precursor, sol composition and applying dip-coating deposition procedure in order to obtain thin films or coatings. All materials were visualized and characterized by the Atomic Force Microcscopy (AFM) technique. Moreover, characterization of titania nanocomposites was extended to the tribological tests performed by means of microtribometer operating in normal loads range of 30–100mN.The AFM analysis of mesoscopic objects and nanoparticles showed that the diameter of synthesized silica nanotubes was 60–70nm and the size of titania nanoparticles was 43nm. In case of porous layers the pore size in titania and zirconia coatings oscillated between 100 and 240nm, however their shape and distribution were irregular.Microtribological studies of nanocomposites revealed the moderate decrease of the coefficient of friction for samples containing 5, 15 and 5wt.% of zirconia nanoparticles in titania coatings annealed at 100, 500 and 1000°C respectively. An enhancement of antiwear properties was already observed for 1wt.% of nanophase content, except the sample annealed at 500°C. It was also found that the annealing at high temperatures is a primary factor which affects the reduction of friction and wear of titania coatings while the presence of nanoparticles has secondary effect.Investigations in this study carried out with the use of the AFM technique highlighted the potential and flexibility of sol–gel approach in designing of various types of advanced materials in a form of mesoscopic objects, porous coatings and composite layers. Results collected in this study clearly demonstrated that sol–gel technique can be applied effectively in preparation of broad range of modern materials.

Keywords: Sol–gel; Nanoobjects; Thin layers; Nanocomposites; AFM

Coating of glass with ZnO via ultrasonic irradiation and a study of its antibacterial properties by Guy Applerot; Nina Perkas; Galina Amirian; Olga Girshevitz; Aharon Gedanken (pp. s3-s8).

Zinc oxide (ZnO) nanoparticles were synthesized and deposited on the surface of glass slides using ultrasound irradiation. The structure and morphology of the nanoparticles were studied as a function of the synthesis time. The deposited film was analyzed using characterization methods such as XRD, SEM, AFM, and optical spectroscopy. Zinc oxide submicron crystals with an average diameter of ∼300nm strongly adhered to the glass surface. This method is fast, simple, convenient, economical, and environmentally friendly. The antibacterial activities of the ZnO–glass composites were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures. A significant bactericidal effect, even in a 0.13% coated glass (wt.%), was demonstrated.

Keywords: ZnO nanoparticles; Glass coating; Ultrasound irradiation; Antibacterial activity

Bromine-containing functional nanolayers for biomolecule immobilization by J.D. McGettrick; T. Crockford; W.C.E. Schofield; J.P.S. Badyal (pp. s30-s34).

Bromine-containing nanolayers are deposited by pulsed plasma deposition of 2-bromoethylacrylate. Subsequent covalent immobilization of single-strand DNA onto these films is achieved via the reaction with a terminal thiol group linker contained in the oligonucleotide.

Keywords: Biomolecule; Immobilization

Fabrication of three-dimensional substrates for Li microbatteries on Si by Arockia Vimal Jeyaseelan; James F. Rohan (pp. s61-s64).

Lithographic techniques for patterning planar substrates to achieve microbattery materials compatible three-dimensional (3D) Ni substrates for sequential deposition of active battery materials are described. A single spin negative photoresist is used to achieve 100μm pattern heights. After patterning, Ni is electroplated on the substrates from a low stress Ni sulphamate bath to a maximum of 100μm. The sidewall angle achieved yields a thinner Ni feature at the surface level than at the base which is a key parameter to facilitate subsequent active battery materials deposition by vacuum deposition techniques. An aspect ratio of 1.5:1 has been achieved and the surface area is increased by comparison with planar electrodes.

Keywords: Microfabrication; 3D; Microbattery; Anode; Silicon; Lithium

Use of a PECVD–PVD process for the deposition of copper containing organosilicon thin films on steel by A. Daniel; C. Le Pen; C. Archambeau; F. Reniers (pp. s82-s85).

A low frequency plasma process is used to deposit thin films on steel through simultaneous sputtering and plasma enhanced chemical vapour deposition (PECVD). The deposited material consists in composite copper–organosilicon thin layers where copper is obtained by magnetron sputtering whereas the organosilicon plasma polymer is grown by PECVD from HMDSO (hexamethyldisiloxane).This paper focuses on the important process parameters required to control the quantity of incorporated copper in the layer, particularly the metalorganic concentration and the sputtering current. The dispersion of copper vs. the thin film thickness is found to be homogeneous. The deposited layers show antimicrobial activity for copper contents higher than X=38%, where X=[Cu]/([Cu]+[Si]).

Keywords: PACS; 81.07.−b; 81.15.−zPECVD; Sputtering; Copper; HMDSO; Steel; Antibacterial

Microbattery technology overview and associated multilayer encapsulation process by R. Salot; S. Martin; S. Oukassi; M. Bedjaoui; J. Ubrig (pp. s54-s57).

Lithium microbatteries with different positive electrode materials (V₂O₅, LiCoO₂, TiOS) in association with a solid electrolyte (LiPONB) and a lithium negative electrode are very promising energy storage systems that can fit all the applications requirements. One of the challenges of the technology is related to the fact that lithium microbatteries are easily degraded in atmosphere. Indeed, these devices require encapsulation with a barrier material, which exhibits extremely low permeation rates for water vapour and oxygen. To obtain such a high barrier, we chose to direct our studies on layers deposited by plasma-enhanced chemical vapour deposition (PECVD), and more particularly on amorphous materials like silicon oxide (SiOx) and silicon nitride (SiNx). Both the active layers of the microbattery architecture and the multilayer encapsulation stack will be discussed.

Keywords: Microbattery; Encapsulation; PECVD; MEMS; Photolithography

Plasma deposition of organosilicon polymer thin films with embedded nanosilver for prevention of microbial adhesion by Claire Saulou; Bernard Despax; Patrice Raynaud; Sandrine Zanna; Philippe Marcus; Muriel Mercier-Bonin (pp. s35-s39).

Composite thin films (∼170nm) containing silver nanoclusters embedded in an organosilicon matrix were deposited by PE-CVD onto stainless steel in order to prevent microbial adhesion. The process originality relies on a dual strategy combining silver sputtering and simultaneous plasma polymerization in argon–hexamethyldisiloxane (HMDSO) plasma, using an asymmetrical RF glow discharge. The metal content in the film was controlled by varying the HMDSO flow rate. Investigation of the physico-chemical properties of the obtained films was conducted by X-ray photoelectron spectroscopy and transmission FTIR spectroscopy. Plasma-mediated coatings were composed of C, O, Si and Ag which was predominantly under metallic form, as indicated by XPS analysis. The presence of Si–H, Si–O–Si, Si–(CH)_n–Si and C–H groups was established by FTIR. The yeast Saccharomyces cerevisiae was selected as the model for eukaryotic microorganisms. The maximal anti-adhesive efficiency was achieved for the organosilicon matrix alone. When nanosilver was incorporated into the organic matrix, the efficiency was reduced, especially for high metal contents. Silver antimicrobial property was assumed to be related to Ag⁺ progressive release from the embedded nanoparticles into the surrounding medium. This release was confirmed by ICP-MS measurements. Moreover, silver-containing film antifungal activity was observed towards sessile cells.

Keywords: PACS; 81.15.−z (Methods of deposition of films and coatings, film growth); 81.15.Cd (Deposition by sputtering); 81.15.Gh (Chemical vapour deposition (including plasma-enhanced CVD, MOCVD, etc.)); 82.35.Np (Nanoparticles in polymers); 87.18.Fx (Multicellular phenomena, biofilms)Microbial adhesion; Stainless steel; Plasma deposition; Thin films; Silver nanoclusters; Organosilicon matrix

Mesoporous silica layers with controllable porosity and pore size by Florian Eder; Nicola Hüsing (pp. s18-s21).

Silica layers with controllable porosity and pore size were prepared via a templating approach. The structure of these mesoporous films was examined by porosimetry via ellipsometry and transmission electron microscopy. A design of experiment (DOE) method was used to gather information about the influence of the processing parameters on the final film structure. A model was developed, allowing a precise control of the pore diameters and porosity of the silica coating.

Keywords: PACS; 42.79.Wc; 68.08.BcThin film; Porosity; Structure and morphology; Optical coatings; Refractive index

Nanostructured waveguides for evanescent wave biosensors by Ana Maria Popa; Bernard Wenger; Emmanuel Scolan; Guy Voirin; Harry Heinzelmann; Raphael Pugin (pp. s12-s17).

Nanostructuring waveguides by means of block-copolymer assisted lithography has as effect an increase in the total surface area. The non-specific adsorption of proteins on the nanostructured surfaces was monitored by wavelength-interrogated optical sensing and an increase in the sensitivity of the detection as compared to flat chips was observed. A model of the adsorption process confirmed the obtained experimental results and allowed the design of experimental approaches through which the detection sensitivity can be further improved.

Keywords: PACS; 81Waveguide; Nanostructures; Block-copolymer lithography; Non-specific adsorption; Sensors; Biosensors

Selected properties of a-C:H PACVD coatings by F. Cerny; V. Jech; S. Konvickova; J. Suchanek (pp. s22-s25).

a-C:H films were deposited by rf PACVD from methane and their growth rate, thermal treatment, morphology, adhesion and electrical passivation properties were investigated. Deposition at room temperature gave the highest film growth rates. The Raman spectra obtained for a-C:H films indicated that the D peak becomes more pronounced as the annealing temperature grows higher. The rf plasma produced a-C:H passivation films which are sufficiently insulating at voltages up to ca. 2200V.

Keywords: PACS; 81.15.−za-C:H films; rf PACVD; Film growth rate; Electrical passivation

Architecture and composition influence on the properties of some smart polymeric materials designed as matrices in drug delivery systems. A comparative study by Cornelia Vasile; Raluca Petronela Dumitriu; Catalina Natalia Cheaburu; Ana Maria Oprea (pp. s65-s71).

Variable architecture polymeric materials have been developed covering interpolymeric complexes (IPC), graft copolymers and hydrogels constituted from natural and synthetic polymers which offer unique properties such as responsivity to temperature and/or pH, biodegradability, specificity, and biocompatibility.The interpolymeric complexes and hydrogels of PNIPAAm with alginate or chitosan behave as “smart” dual-responsive materials with transition temperature/pH values close to the physiological ones.This new class of interpolymeric complexes, graft copolymers and hydrogels can sense environmental changes in the physiological range and it has found application in drug delivery in which subtle pH/temperature differences are important. Drug delivery systems have been prepared and tested with good results. Kinetics of the swelling/loading and release of some drugs have been also evaluated.

Keywords: Smart; PNIPAAm; Alginate; IPC; Grafted copolymer; Hydrogel; Drug delivery

Editorial Board (pp. ii).

Processes and structures for generation of hydrophobic surfaces for large-scale and industrial operations by S. Kamps; W. Ensinger; F. Eder; A. Berndt; H. Zeininger (pp. s92-s95).

Common industrial processing procedures have been used to introduce surface structures into hydrophobic surfaces. In this paper, four different concepts (stamping, spraying, grinding and sandblasting) are evaluated regarding their applicability for large-scale production. In comparison to surfaces with equal hydrophobic properties the mechanical stability was improved.

Keywords: PACS; 68.35.Ct; 68.08.BcHydrophobic surface; Contact angle; Structuring; Roughness; Thin film

Infrared Spectroscopic Ellipsometry analysis of Nano-structured thin films in polymers and semiconductors by Jean Louis Stehle; Jean Philippe Piel (pp. s72-s76).

Spectroscopic ellipsometry has long been recognized as a powerful technique to characterize thins films and multilayer structures. It is now routinely used for non-destructive on-line characterization of semiconductor process. SOPRALAB leader in commercial spectroscopic ellipsometry for research and development, has already developed an infrared ellipsometer as an option on visible instrument to provide the largest wavelength range available up to now (from deep UV 190nm to far infrared up to 28μm). The instrument is presented here which includes a small spot size to get ride of the problems of back face reflection on silicon wafers, and an improved signal/noise ratio to allow rapid measurements compatible with an industrial environment. Some examples of application concerning thin films in polymer, dopant density, conductivity and sheet resistance in epilayers, composition of low k dielectrics and polymers are presented.

Keywords: Spectroscopic ellipsometry; Infrared; Low; k; dielectrics; Epitaxial structures; Dopants

Physical surface adsorption and Molecular Surface Fractal Analysis (MFSA) detected with Spectroscopic Ellipsometry by F. Ferrieu; J.P. Piel; J.L. Stehlé (pp. s96-s100).

It is known for years that surface adsorption/desorption can be studied by in situ Spectroscopic Ellipsometry (SE). The physical adsorption of water or other small adsorbate molecule species on the surface of non-porous materials, gives rise to a Type II isotherms which can be measured with sufficient accuracy by SE. The paper reports on recent highlights of this promising application of SE for Molecular Surface Fractal Analysis (MFSA) with a high sensitivity. It is reconsidered with the fractal description of surfaces. The adsorption theories including the effect of fractal properties of thin films surfaces have been recently reviewed and corresponding models can be specifically applied to SE analysis. Within the concept of the surface fractal properties, the study of surface adsorption provides interesting parameters such as dimensionality and surface energy parameters to be correlated with other instrumental observations. Some examples are presented and discussed.

Keywords: Fractal; Ellipsometry; Molecular Surface Analysis; Adsorption

Fabrication of superhydrophobic surfaces with controlled topography and chemistry by N. Blondiaux; E. Scolan; A.M. Popa; J. Gavillet; R. Pugin (pp. s46-s53).

We report the fabrication of sub-micrometer large silicon pillars with controlled aspect ratios by combining thin polymer film structuring and dry etching. A wide library of structures was achieved thanks to the tunability of the process both concerning lateral and vertical dimensions. The structures were further used to create superhydrophobic surfaces. Depending on the aspect ratio of the pillars, different superhydrophobic wetting states were observed. Special attention was also paid to the influence of surface structuring on the contact angle hysteresis.

Keywords: PACS; 81 Material ScienceSuperhydrophobicity; Polymer demixing; Nanolithography; Contact angle hysteresis; Cassie–Baxter; Wenzel

Ellipsometry porosimetry (EP): Thin film porosimetry by coupling an adsorption setting with an optical measurement, highlights on diffusion results by A. Bourgeois; Y. Turcant; Ch. Walsh; Ch. Defranoux (pp. s26-s29).

Ellipsometry porosimetry (EP) is an emerging technique that is dedicated to porous thin films analysis; it is non-contact and non-destructive. EP tools developed at SOPRALAB, allows us to obtain adsorption isotherms with many different adsorptives at an ambient temperature. EP leads to the same results as classical adsorption experiments (e.g. porosity and pore size distribution), but it also has some particular features leading to new information. For instance, our optical setup (Spectroscopic Ellipsometry) allows us to determine the variation of the thickness of the samples during the adsorption experiment. It is also very sensitive to interfaces; it is thus possible to detect a porosity gradient or to study a bi-layer sample and plot the two corresponding adsorption isotherms at the same time [A. Bourgeois, A. Brunet-Bruneau, V. Jousseaume, N. Rochat, S. Fisson, B. Demarets, J. Rivory, Description of the porosity of inhomogeneous MSQ films using solvent adsorption studied by spectroscopic ellipsometry in the visible range, Thin solid films 455–456 (2004) 366]. For porous thin films with a non-porous barrier layer deposited on top, it is also possible to study the lateral diffusion phenomenon in the film (see figure below). In this paper, we will illustrate a part of the different features of EP for adsorption on porous thin films and more particularly for diffusion phenomenon.

Keywords: Adsorption; Porous; Diffusion; Barrier layer

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Applied Surface Science (v.256, #3)